Drill head with hydraulic thrust balancing means



May 12, 1959 w. o. NlxoN DRILL HEAD WITH HYDRAULIC THRUST BALANCING MEANS Filed April 30, 1956 United States Patent DRILL HEAD WITH HYDRAULIC THRUST BALANCINGMEANS William O. Nixon, Ferndale,`Mich.

Application April 30, 1956, Serial No. 581,638

2 Claims. ('Cl. 285-94) This invention relates to hydraulic drill heads, and more particularly to devices adapting deep-drilling tools for use with conventional drill presses.

The problems involved in drilling small diameter and very deep holes in metal have required the development of new techniques especially adapted for deep hole drilling. So-called gun drills have been in common use for this purpose. Such drills have axial oil holes and are held in the ends of tubes which run through guide bushings. A longitudinal groove is provided in the drill and tube, and the oil pumped at high pressure forces the chips back through this groove.

In some types of work, gun drillsare mounted in special lathe-type machines so that the work is rotated during drilling. There are many lcases however in which the job does not warrant the expense of a special machine of this type, but where the operator desires to utilize aconventional drill press for the deep-drilling operation. Various adaptors have been developed for this purpose, by means of which the gun drill tube may be connected to the spindle of the drill press and supplied with high pressure oil.

Devices of this type provided in the past have had various disadvantages making them unsatisfactory under actual shop conditions. The conventional attachment utilizes a stationary collar member or head mounted onrthe spindle with seals provided between the head and spindle to prevent leakage. It has been found very difficult to overcome the eifects of wear on these seals under the high speed conditions of modern gun drilling operations. It has also been found necessary with conventional attachments to provide axial stops limiting movement of the head due to pressure differentials on the radial surfaces thereof. Such differentials may be produced by dimensional variations in the head bores, and the friction produced between a rotating stop and its abutting head surface may seriously detract from the efficiency of tool operation, and drill head life.

It is an object of the present invention to overcome the disadvantages of previously known hydraulic drill heads of this type and to provide a device which has no Wearing parts and produces no friction which could hamper the operational eiciency of the drill.

It is a further object to provide an improved hydraulic drill head of the above nature, which utilizes the oil pressure supplied to the drill for the purpose of maintaining a friction-free oating condition of the head, the head position being automatically adjustable to allow for dimensional variations in the various bores thereof.

lt is also an object to provide an improved hydraulic drill head of this character, which utilizes the oil ow between the stationary and rotating parts of the device for coolant purposes, thus preventing overheating of the drill head parts and at the same time resulting in no loss of oil in the system.

It is another object to provide an improved hydraulic drill head of the above nature which is adapted to prevent oil leakage even after portions of the device have lCC ' 2 been worn, and which may utilize for this purpose the oil pressure supply system itself.

Other objects, features and advantages of the present invention will become apparent from the subsequent description taken in conjunction with the accompanying drawing. l

The gure is an elevational view in cross section of the novel drill head of this invention, with a schematic showng of a hydraulic system adapted to cooperate with the ead.

The drill head comprises a spindle generally indicated at 11 having an upper portion 12 adapted to be connected to the drive shaft of a conventional drill press, this shaft being shown partially in dot-dash lines at 13. Spindle 11 is continuously rotatable during drill operation and is provided with a central bore 14 at its lower end within which a gun drill, shown partially in dot-dash lines at 15, may be secured. A stator generally indicated at 16 surrounds the central portion 17 of spindle 11, this stator comprising a centralportion 18a top portion 19 and a bottom portion 21. A plurality of bolts 22 are provided for securing together the portions of stator 16 so that adjacent portions are in fluid-tight relation, and the stator is adapted to be secured by appropriate means (not shown) to a stationary portion ofthe drill press in such a manner as to permit axial movement thereof. An upper stop collar 23 and a lower stop collar 24 are mounted on spindle 12 by threads or other appropriate means above and below stator 16, the spacing of these collars being such that limited axial movement of the stator on the spindle is permitted.

Means are provided in stator 16 and spindle 11 for supplying high pressure oil to bore 14 within which gun drill 1S is secured. In particular, central portion 18 of the stator is provided with spaced. upper and lower bores 25 of equal diameter and a central bore 26 having a diameter somewhat less than that of the upper and lower bores. Spindle 11 is formed with spaced upper and lower shoulders having annular radial surfaces 27 and 28 respectively in facingyrelation, these surfaces being spaced apart a distance slightly less than the length of central bore 26. The shoulders are further provided respectively with cylindrical surfaces 29 and,30 having aloose sliding lit within bore 26. With stator 16 in its central position with respect to spindle 11 as shown in the figure, the parts will together form a central annular chamber 31 between surfaces 27 and 28, and will also form upper and lower chambers 32 and 33 respectively above and below the central chamber. Because of the slight clearance between surfaces 29 and 30 and central bore 26 of the stator, restricted annular leakage paths 35 and 36 will exist between chamber 31 and upper and lower chambers 32 and 33 respectively, the relative lengths of these leakage paths as well as their cross-sectional orifice areas being of course dependent upon the particular axial position of stator 16 with respect to the spindle. With stator 16 against upper collar 23, chambers 31 and 33 will be connected by a relatively unrestricted ow path, whereas with stator y16 in its lower position againstrcollar 24 central chamber. 31 will be connected unrestrictedly with chamber 32.

An inlet port 37 is provided in central portion 18 of the stator for supplying high pressure oil to central chamber 31. Spindle 11 is provided with a radial passageway 38 connected with chamber 31 and an' axial passageway 39 leads from passageway 38 to the upper end of bore 14. A sealing member 41 may be provided at an intermediate portion of bore 14 for preventing oil leakage along the outside of the ygun drill shank, the latter being securable in bore 14 by'rneans of a set screw 42.

Upper section 19 of the stator is provided with annular grooves 43 and 44. In particular, groove 43 of this section is adjacent chamber 32, being separated therefrom by a land 45, whereas groove 44 is adjacent the upperA end of sect-ion 19, being separated therefrom by a land 46.` 'Grooves 43 and 44 are themselves separated by an intermediate land 47. Likewise, lower section 21 of the stator is provided with 4a groove 48,separated by a land `49 from` chamber 33 and by a land 51 from a groove 52, the latter being in turn separated by a land y53 from the lower end of section 21. y"Lands 45, `46, 47, 49, 51 and 53 are of such diameter as to provide a normal running clearance between stator 16 and spindle 11.

Leading from groove `44 of upper stator section 19 and from groove 52 of lower section 21 are a pair of passageways 54 and 55y respectively, these passageways being connected with anaxially disposed passageway 56 in -central section `18 of the stator. An outlet port 57 is provided ingcentral section 18v of the stator for disposing "ofoil which` passes through the system of chambers, lgrooves and passageways described above.

A suitable system for supplying and removing high 'pressure oil from the mechanism is shown schematically in the iigure, it being understood that other arrangements for this purpose are contemplated within the scope of the invention. The system shown comprises a gear pump 58 supplied by a tank 59 through a conduit 61 and having v'a supply conduit 62 leading to port 37. A by-pass convduit 63 having a pressure relief valve 64 may be provided for pump 58 and a return conduit 65 is connected between loutlet port 57 of stator 16 and the pump. A restriction l66 in the form of a iixed resistance is provided in conduit 61 so that the pressure at the juncture 67 of conduits 61 and 65 will be less than atmospheric. This sub-atmos- 'pheric pressure will be transmitted to grooves 44 and 52 of the stator so that oil passing into these grooves will be removed through passageways 54, 55 and 56.

In operation, the parts when at rest without oil pressure being applied to the unit will be so disposed that lthe bottom of stator 16 rests on lower stop collar 24. This position will be naturally assumed because of the weight of stator 16, and will result in central chamber 31 -being connected with chamber 32 whereas chambers 31 'and 33 will be connected only through restricted area 36 formed by the overlapping portionsof surface 30 and bore 26. After gun drill has been secured within bore 14 pump 5S will be operated and spindlerll will be rotated by drive-shaft 13. Oil will flow from tank 59 to conduitv 61, pump `58 and conduit 62 tov inlet port 37 of the stator. From the inlet port the oil will ovv into chamber 31 and thence through passageways 38 and 39 of spindle 11 to the upper end of gun drill 15 Within bore 14.

At thesame time, oil will tend to flow from central chamber 31 to upper and lower chambers 32 and 33 respectively, and thence past the various lands and grooves of the upper and lower sections of the stator. Because of the relatively unrestricted connection between chambers 31 and 32 as compared with the restricted connection between chambers 31 and 33, the pressure in chamber 32 will become higher than that in chamber 33. The differential in pressures against radial surfaces 68 an-d 69 of these two chambers respectively will result in an upward force on stator 16, tending to lift it away from lower stop collar 2:4. As this movement takes place, the overlap 36 between surface 30 and bore 26 will lessen whereas the overlap 35 between surface 29 and bore 26 will appear and begin to increase. This phenomenon 'will cause an alteration inthe relative pressures between chambers 32fandg33, since the oil ltending to flow from central chamber 31 into the upper and lower chambers will 4meet'resistances which are more equal than before. When stator 16. hasv reached an axial position with respect to spindle `11 which, taking into account the weight of the stator,results inl equal and opposite axial forces on the stator, the latter will stabilize itself at this axial position. The dimensions of the parts are such that stator 16 will in itsxnormal operating position be spaced from occur during manufacture of the device.

both collars23 and 24, so that no friction will be produced between the stator and spindle, other than that due to the viscous effect of the oil between the stationary and rotating parts.

The oil leaving upper and lower chambers 32 and 33 (the amount being independent of the volume fed to the drill) will enter between the lands of the upper and lower sections respectively of stator 16, passing through the grooves of these sections and into outlet passages 54, 55 and 56. The oil will thence flow through outlet port 57 and conduit 65 back into the hydraulic system. Normally, the oil pressure will be reduced during its passage through these lands and groovesto'such an extent that it will not have suicient force to flow past upper and lower end lands 46 and 53 of the stator. However, if after considerable running time lands 46 and 53 should become worn, the danger of such oil leakage into the atmosphere could increase. For this reason, the presence of restriction 66 in conduit 61, and the subsequent subatmospheric pressure in grooves 44 and 52 will serve to prevent such oil leakage outside the stator itself.

It should be observed that the construction of the novel drill head is such as to inherently compensate for variations in dimensions of the various bores which may Because the overlaps 35 and 36 between thespindleshoulders and central bore will automatically be adjusted to provide equal forces on the spindle, such dimensional variations will not have a deleterious eifect on operation of the device. It should also be observed that the continuous ow of oil through the device at all times will perform a cooling function so that the overheating of the device will be lessened. The unit eliminates any mutually conf tacting parts which might result in frictional wear and loss of power during drilling. Furthermore, the application of axial pressure to the spindle during the drilling operation will in no way interfere with the principle of operation described above, since such forces will pass directly to the tool.

While it will be apparent that the preferred embodiment of the invention disclosed is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the sub-joined claims.

, What is claimed is:

l. In a hydrauhc drill head, a spindle, an axial bore at the lower end of said spindle for receiving a drill shank, a fluid passageway leading inwardly from a central portion of said spindle to the upper end of said bore, a stator surroundingsaid spindle and slidable thereon, a pair of stops on said spindle above and below said stator and spaced apart a distance slightly greater than the length of said stator, an annular central chamber formed between said stator and spindle and connected with said fluid passageway, an inlet port in said stator connected with said central chamber, annular upper and lower chambers formed between said stator and spindle, the ystator and spindle having two pairs of closely adjacent annular surfacesbetween said central chamber and said upper and lower chambers respectively, the stator being `,disposable in a central position spaced from said stops in which said two pairs of surfaces are in overlapping relation to` restrict Huid flow from said central chamber to said upper and lower chambers, the stator being movable axially from said central position in either direction to a position in which iiow from said central chamber to one of said upper and lower chambers is relatively unrestricted, and means for permitting'iluidV flow .from said upper and lower chambers, whereby uid pressure applied to said inlet port will urge said stator toward its central position. Y f I K 2. in a hydraulic dr-ill head, a spindle, an axial bore at the lower end of said spindle for receiving a drill shank, a fluid passageway leading inwardly from a central portion of said spindle to the upper end of said bore, a stator surrounding said spindle and slidable thereon, a pair of stops on said spindle above and below said stator and spaced apart a distance slightly greater than the length of said stator, an annular central chamber formed between said stator and spindle and connected with said fluid passageway, an inlet port in said stator connected with said central chamber, annular upper and lower chambers formed between said stator and spindle, the stator and spindle having two pairs of closely adjacent annular surfaces between said central chamber and said upper and lower chambers respectively, the stator being disposable in a central position spaced from said stops in which said two pairs of surfaces are in overlapping relation to restrict uid ow from said central chamber to said upper and lower chambers, the stator being movable axially from said central position in either direction to a position in which fluid ow from said central chamber to one of said upper and lower chambers is relatively unrestricted, a plurality of alternate lands and grooves formed between said stator and spindle above said upper chamber and below said lower chamber, said lands and grooves permitting restricted ow of uid outwardly from said upper and lower chambers, and connections from the outermost of said grooves for permitting uid to be drawn off therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 696,655 Ray Apr. 1, 1902 1,020,699 Kieser Mar. 19, 1912 1,323,412 Schorr Dec. 2, 1919 1,323,474 Hodgkinson Dec. 2, 1919 1,488,931 Marechal Apr. 1, 1924 1,728,268 Flanders Sept. 17, 1929 1,779,076 Ray Oct. 21, 1930 1,827,866 Allen Oct. 20, 1931 1,873,988 Van Rijswijk Aug. 30, 1932 2,721,747 Whitfield Oct. 25, 1955 2,777,702 Rodal Jan. 15, 1957 FOREIGN PATENTS 907,256 France June 18, 1945 

